ttf_parser/tables/
hvar.rs

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1// https://docs.microsoft.com/en-us/typography/opentype/spec/hvar
2
3use core::convert::TryFrom;
4
5use crate::{GlyphId, NormalizedCoordinate};
6use crate::parser::{Stream, Offset, Offset32};
7use crate::var_store::ItemVariationStore;
8
9#[derive(Clone, Copy)]
10pub struct Table<'a> {
11    data: &'a [u8],
12    variation_store: ItemVariationStore<'a>,
13    advance_width_mapping_offset: Option<Offset32>,
14    lsb_mapping_offset: Option<Offset32>,
15}
16
17impl<'a> Table<'a> {
18    pub fn parse(data: &'a [u8]) -> Option<Self> {
19        let mut s = Stream::new(data);
20
21        let version: u32 = s.read()?;
22        if version != 0x00010000 {
23            return None;
24        }
25
26        let variation_store_offset: Offset32 = s.read()?;
27        let var_store_s = Stream::new_at(data, variation_store_offset.to_usize())?;
28        let variation_store = ItemVariationStore::parse(var_store_s)?;
29
30        Some(Table {
31            data,
32            variation_store,
33            advance_width_mapping_offset: s.read::<Option<Offset32>>()?,
34            lsb_mapping_offset: s.read::<Option<Offset32>>()?,
35        })
36    }
37}
38
39
40pub struct DeltaSetIndexMap<'a> {
41    data: &'a [u8],
42}
43
44impl<'a> DeltaSetIndexMap<'a> {
45    #[inline]
46    pub fn new(data: &'a [u8]) -> Self {
47        DeltaSetIndexMap { data }
48    }
49
50    #[inline]
51    pub fn map(&self, glyph_id: GlyphId) -> Option<(u16, u16)> {
52        let mut idx = glyph_id.0;
53
54        let mut s = Stream::new(self.data);
55        let entry_format: u16 = s.read()?;
56        let map_count: u16 = s.read()?;
57
58        if map_count == 0 {
59            return None;
60        }
61
62        // 'If a given glyph ID is greater than mapCount-1, then the last entry is used.'
63        if idx >= map_count {
64            idx = map_count - 1;
65        }
66
67        let entry_size = ((entry_format >> 4) & 3) + 1;
68        let inner_index_bit_count = u32::from((entry_format & 0xF) + 1);
69
70        s.advance(usize::from(entry_size) * usize::from(idx));
71
72        let mut n = 0u32;
73        for b in s.read_bytes(usize::from(entry_size))? {
74            n = (n << 8) + u32::from(*b);
75        }
76
77        let outer_index = n >> inner_index_bit_count;
78        let inner_index = n & ((1 << inner_index_bit_count) - 1);
79        Some((
80            u16::try_from(outer_index).ok()?,
81            u16::try_from(inner_index).ok()?
82        ))
83    }
84}
85
86#[inline]
87pub(crate) fn glyph_advance_offset(
88    table: Table,
89    glyph_id: GlyphId,
90    coordinates: &[NormalizedCoordinate],
91) -> Option<f32> {
92    let (outer_idx, inner_idx) = if let Some(offset) = table.advance_width_mapping_offset {
93        DeltaSetIndexMap::new(table.data.get(offset.to_usize()..)?).map(glyph_id)?
94    } else {
95        // 'If there is no delta-set index mapping table for advance widths,
96        // then glyph IDs implicitly provide the indices:
97        // for a given glyph ID, the delta-set outer-level index is zero,
98        // and the glyph ID is the delta-set inner-level index.'
99        (0, glyph_id.0)
100    };
101
102    table.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
103}
104
105#[inline]
106pub(crate) fn glyph_side_bearing_offset(
107    table: Table,
108    glyph_id: GlyphId,
109    coordinates: &[NormalizedCoordinate],
110) -> Option<f32> {
111    let set_data = table.data.get(table.lsb_mapping_offset?.to_usize()..)?;
112    let (outer_idx, inner_idx) = DeltaSetIndexMap::new(set_data).map(glyph_id)?;
113    table.variation_store.parse_delta(outer_idx, inner_idx, coordinates)
114}
ttf_parser/tables/hvar.rs

ttf_parser/tables/
hvar.rs
